Second author

Formation of the Antarctic Ice Sheet was set in motion some 34 million years ago, when atmospheric carbon dioxide levels dropped drastically, causing rapid global cooling. However, it remains unclear how early glaciation events developed into a continent-sized sheet of ice. On page 690, an international team of scientists use ice-penetrating radar to pinpoint the centre of the ice sheet's growth. Beneath 3,000 metres of ice, they describe a picturesque landscape, akin to that of the Alps, that has remained unchanged for at least 14 million years. Martin Siegert, a glaciologist at the University of Edinburgh, UK, tells Nature more.

How did this collaboration come about?

At a meeting in France in 2002, I met lead author Sun Bo of the Shanghai-based Polar Research Institute of China, and he then visited me for a year at the University of Bristol's Glaciology Centre, where I was director. We gave him access to the largest existing data set of Antarctic ice-penetrating radar, collected by aircraft in the 1970s. He spent two years planning a field survey of the region at the centre of the ice sheet, named Dome A, that overlies the Gamburtsev Mountains. He wanted to map the subglacial landscape in this remote location and, in so doing, document the early events of glaciation, as a way of advancing China's ambitious Antarctic research programme.

Was it difficult to survey the region?

Yes. The conditions are so extreme that few people have ever visited the site. It is a desperately cold place at high altitude, set more than 4 kilometres above sea level. Sun Bo and his colleagues drove snowmobile sleds carrying radar survey equipment from the ice sheet's edge to its centre to survey an area 30 kilometres square around Dome A. This was no small achievement.

What can the Alp-like topography tell us?

That it was carved during two earlier smaller-scale glacial phases and then preserved under a large sheet of ice. The lack of erosion that had occurred since the ice sheet formed allowed Sun Bo and I to determine that these early glaciation features would have formed at about 3 °C. Because the records we have contain no evidence of Antarctic temperatures being near that level during the past 14 million years, we know that the ice sheet is at least that old.

Does this work shed light on current climate change?

It provides an understanding of how little the Antarctic Ice Sheet has changed over 14 million years, during which carbon dioxide levels have been relatively stable.